1. Field of the Invention
The present invention relates to a double glazed window having a blind between double panes of glass.
2. Description of the Prior Art
It is well known in the art that double panes of glass in a window provides better insulation than a single pane of glass. It is also known in the art to provide venetian type blinds or pleated shades between two panes of glass. A pleated blind between window panes is disclosed in the U.S. Pat. No. 4,913,213 to Schnelker. A venetian or slat blind between panes of glass is disclosed in the U.S. Pat. Nos. 4,687,040; 4,664,169 and 5,379,825. Control means for lifting, lowering and tilting the blind from one side of the window must be provided while maintaining the window seal. The art has provided cords and cables, sometimes driven by a motor or gear system, as the control means. The most popular systems route the cord through an aperture drilled through the interior pane of glass.
U.S. Pat. No. 4,687,040 to Ball discloses a device for adjusting the tilt angle of slats of a slat blind positioned between the panes of glass. The device includes a hole in one pane of glass and a flexible cable passing through the hole. The cable is connected to a rectangular member which controls the rotation of the slats. When the cable is turned by external torque, the slats are tilted.
U.S. Pat. No. 4,913,213 discloses a pleated blind between double window panes and blind control means for raising and lowering the blind. One embodiment is comprised of an aperture in one pane of glass and a bolt with a center hole mounted in the aperture. An actuator cord passes through the bolt hole and further up and over a screen, if desired, thereby providing an external control mechanism.
The prior art has also developed more complicated control means that utilize cables and gear systems that pass through the window frame rather that the glass. U.S. Pat. No. 4,664,169 to Osaka et al. discloses a device for tilting slats of a venetian blind between double panes of glass. The device uses electrical power driving means to move piezoelectric bimorph device in a horizontal plane. The piezoelectric bimorph device is mounted to a block having a threaded bore. The piezoelectric bimorph device mechanically moves an elongated V-shaped beam under two cross arms which control the rotation of the slats. When the beam is moved, the cross arms are tilted, thereby rotating the slats.
The complicated systems that require control means to be mounted in or routed through the window frame are relatively expensive to manufacture. Furthermore, in many of these systems gears and motors wear and then slip or fail. Many of these control devices require a headrail which is too wide to fit between the panes of those windows whose panes are not more than 3/4 inches apart. Hence, these systems have never achieved the popularity of through the glass systems. Those systems which require apertures to be drilled or cut through the glass are disliked by manufacturers because breakage of the glass during drilling and assembly is common.
The problems of the prior art systems discussed above are not present if the control means is a cord or cords routed between the edge of the interior glass panel and the window frame. In U.S. Pat. No. 4,913,213 Schnelker describes a pleated blind between window panes. In a second preferred embodiment the actuator cord is routed over the glass housing and any screen housing provided. An L-shaped guide having a single vertical and horizontal channel cut therein is fitted over the top edge of the glass housing. An actuator cord passes through the channel. A major problem with this system is that one cannot maintain a seal between the window frame and the edge of the glass housing. Another problem is that most blinds have four control cords, two lift cords and two tilt cords. If all four cords are routed through a single channel they tend to bind and interfere with one another.